Figure 2

Pairwise variation V_n/n+1between the normalizing factors NF _n and NF _{n +1} The variation V_n/n+1between NF _n and NF _{n +1} was calculated with geNorm to determine the optimal number of reference genes that should be used for normalization. The empirical cut-off value 0.15 defined by Vandensompele et al. [6] is marked by a thick line. The lowest variability is marked with an arrow.